Subterranean electrodes are routinely placed in the surface of the earth for various physiochemical, electrical or acoustical applications. One common method for using such subterranean electrodes includes the creation of vitrified underground structures which contain or otherwise encase hazardous waste material. Heretofore, the method of isolating contaminated material at waste sites containing various types of waste was to make barriers, such as concrete retaining walls and plastic lined structures to enclose or otherwise contain the hazardous material. Such structures as a general matter do not have the durability and effectiveness of vitrified soil. Still further, the prior art techniques of providing such artificial barriers had attendant shortcomings such as the requirement to remove soil and waste materials before the creation of the structure. Such handling steps were expensive and often involved the possibility of hazardous waste exposure for the construction personnel or releasing hazardous materials or gases into the ambient environment.
Solidification of soil by in-situ melting and vitrification using heat generated in the soil itself between spaced electrodes has long been known and has been discussed in earlier prior art patents such as U.S. Pat. Nos. 4,376,598, and 5,114,277, the teachings of which are incorporated by reference herein. The prior art method of vitrification is shown in FIG. 1 in the drawings, and which shows a typical arrangement whereby a plurality of electrodes are placed in a position surrounding the region of soil which needs to be vitrified, and thereafter, an electrically conductive pathway is established between the electrodes and immediately below the surface of the ground. Thereafter, electricity is applied to the electrodes with the result that the soil and regions between the electrodes is heated to a temperature where vitrification takes place.
While the prior art practice of vitrification, noted above, has worked with a great deal of success, there are many shortcomings attendant with prior art practices and other devices utilized with same. For example, at some hazardous waste sites, the hazardous material is buried in long continuous trenches and the process of vitrification of the entire trench takes a considerable period of time. As seen in FIG. 1, a housing or outgasing hood is placed over the top of the area of soil being vitrified in order to entrap gases which are produced during the vitrification process. As should be appreciated, as the entire trench area is being processed, it becomes important to align the electrodes such that one region of vitrification may align with and be joined to an adjacent vitrified region such that hazardous material within the trench is completely enclosed. The proper alignment of these electrodes therefore becomes increasingly difficult when they are placed along extended trenches. In addition to the foregoing, the placement of the electrodes in the earth, and thereafter the electrical coupling of the electrodes to the subterranean soil has often been done with some degree of difficulty. For example, in the prior art practice, a bore hole was made in the surface of the earth, and often, before the electrode was placed in the bore hole, the sidewalls of the bore hole would collapse. This would, of course, lead to further excavation. Still further, it has often been difficult to make a good electrical connection between the electrode and the surrounding earthen soil. Moreover, the creation of an electrically conductive pathway between the electrodes often merely consisted of forming a shallow electrically conductive pathway in the surface of the earth as seen in FIG. 1.
Therefore, the present invention relates to a novel method for the placement of subterranean electrodes and electrode pathways which avoids the shortcomings attendant with the prior art practices.